Search

The purpose of this study was to investigate the effects of static (SBT), quasi-dynamic (QDBT), and dynamic (DBT) balance training on balance and muscle power performance in prepubertal children. Randomized, controlled trial design. Fifty-six children (10 and 11 years) were randomly assigned to static (n = 14), quasi-dynamic (n = 14) and dynamic balance training (n = 15), or a control group (n = 13). One-legged static (i.e., unipedal stance on stable surface), quasi-dynamic (i.e., unipedal stance on unstable surface), and dynamic balance (i.e., jumping and stabilizing in unipedal stance on unstable surface) were assessed using two dependent variables, i.e., center of pressure surface area (CoP SA) and velocity (CoP V) with opened (OE) and closed (CE) eyes; as well as lower limbs muscle power (i.e., standing long jump test [SLJ] and countermovement jump [CMJ height]). A significant group × test interactions were observed for static (CoP SA OE; p < 0.05, d = 1.18), quasi-dynamic (CoP SA CE; p < 0.05, d = 0.80), dynamic (CoP V CE; p < 0.05, d = 0.87) balance and power (SLJ [p < 0.05, d = 0.87] and CMJ height [p < 0.01, d = 2.66]) tests. Post hoc analysis showed that DBT demonstrated greater improvement in the measure of balance (p < 0.05, d = 0.80 to 5.17) and power (p < 0.05, d = 2.66 to 3.65) performance. To enhance balance and muscle power performance in prepubertal children, it appears that the level of difficulty in balance training may influence the observed effects. [ABSTRACT FROM AUTHOR]

Evolution of anti-predatory strategies is often associated with specific morphological traits that affect escape or fight performance and ultimately determine survival. Accordingly, good morphological predictors of performance enable inferences of phenotypic evolution in the context of anti-predatory responses. In this study, we evaluated relationships between morphology and performance in South American true toads of Rhinella considering two anti-predatory strategies described for the genus: active escape and chemical defense. Data on morphology, jumping performance and volume of released poison were obtained for 11 Rhinella lineages, and relationships were tested using phylogenetic methods. We identified that the volume of poison released increases with the area of poison glands, and relative hindlimb length is a good predictor of the relative distance jumped. Ancestral reconstructions of performance traits (jumping distance and poison volume) suggest that some Rhinella lineages specialized in one of these anti-predatory strategies (either escaping or producing large amounts of poison), a result that stimulates future studies addressing evolutionary relationships between morphology, ecology and anti-predatory responses in true toads. [ABSTRACT FROM AUTHOR]

[Display omitted] • A soft body detonation driver can be used to design a novel and efficient frog-like jumping robot. • The detonation reaction of the hydrogen–oxygen gas mixed in the soft body cavity is controlled to simulate the explosive force of the frog's hindlimbs during jumping. • Controlling the motion state of the forelimb mechanism to simulate the change of the starting posture angle of the frog in jumping. • Our frog-like jumping robot with a soft-body detonation drive has a jumping dynamic similarity with frogs. Inspired by the instantaneous power of the hindlimbs of frogs and the dexterous posture adjustment of their forelimbs, a frog-like jumping robot based on a soft body detonation drive was designed. By combining the flexibility of silicone material and the detonation characteristics of mixed hydrogen–oxygen gas, a soft body detonation driver was constructed to cause the robot to jump from the hindlimbs to achieve a high energy instantaneous explosive force. Moreover, a spring-based forelimb mechanism is designed. This mechanism not only adjusts the robot with different starting jump posture angles but also maintains a smooth landing by providing cushioning. The kinematics and efficiency models of jumping are also established by the D-H parameter method and geometric method, and they are verified and analysed. Finally, combined with the control system, an experimental prototype (weight 495 g) with a height of 135 mm, a trunk length of 120 mm, front and hindlimbs of 195 mm, and a width of 90 mm is developed. The experiment proved that the robot can not only achieve 6 consecutive jumps, a single jump height of 0.6 m and a spanning distance of 1.2 m but also easily cross rectangular obstacles. [ABSTRACT FROM AUTHOR]

Summary Objective The aim of this study was to compare anthropometric, body composition, and leg power performance in male and female, elite, and national fencers of all age competitive groups and discipline practiced. Subjects and methods A total of 125 fencers (mean ± SD; age 20.6 ± 6.7 years, height 173.2 ± 9.2 cm and body mass 64.7 ± 4.7 kg) participated in this study. Anthropometric measurements were taken before participants performed squat, countermovement, drop, and standing log jump. Results Significant differences were identified between male and female for height (177.6 ± 8.9 cm vs. 167.9 ± 6.2 cm, P < 0.001), body mass (70.4 ± 11.9 kg vs. 57.6 ± 7.0 kg, P < 0.001), arm span (181.8 ± 9.7 cm vs. 168.8 ± 7.2 cm, P < 0.001), leg length (88.9 ± 6.4 cm vs. 81.7 ± 4.3 cm, P < 0.001) and body mass index (22.2 ± 3.0 vs. 20.5 ± 2.1, P < 0.001) and for long jump (202.2 ± 34.7 cm vs. 167.4 ± 23.5 cm, P < 0.05), squat jump (26.5 ± 7.13 cm vs. 19.9 ± 4.00 cm, P < 0.05), counter movement jump (30.1 ± 7.4 cm vs. 21.7 ± 4.5 cm, P < 0.05), drop jump (28.4 ± 9.5 cm vs. 22.3 ± 6.4 cm, P < 0.05) and reaction strength index (0.90 ± 0.4 vs. 0.66 ± 0.3, P < 0.05), respectively. Significant differences in jumping performance were observed between the 14–17 years old and the > 20 years old group for long jump (179.2 ± 30.8 cm vs. 205.2 ± 33.9 cm, P < 0.05), squat jump (21.9 ± 5.3 cm vs. 26.2 ± 7.8 cm, P < 0.05), counter movement jump (25.1 ± 5.9 cm vs. 29.0 ± 8.6 cm, P < 0.05), drop jump (19.01 ± 7.0 cm vs. 25.2 ± 6.7 cm, P < 0.05) and reaction strength index (0.69 ± 0.35 vs. 0.96 ± 0.32, P < 0.05) and between the 18–20 years old > and the 20 years old group for long jump (174.0 ± 30.3 cm vs. 205.2 ± 33.9 cm, P < 0.05), squat jump (22.6 ± 6.1 cm vs. 26.2 ± 7.8 cm. P < 0.05), countermovement jump (24.9 ± 7.1 cm vs. 29.0 ± 8.6 cm, P < 0.05), drop jump (20.9 ± 6.8 cm vs. 25.2 ± 6.7 cm, P < 0.05) and reaction strength index (0.71 ± 0.4 vs. 0.96 ± 0.32, P < 0.05), respectively. Elite fencers performed better in squat (27.3 ± 7.1 cm vs. 22.9 ± 6.5 cm, P < 0.05), countermovement jump (30.5 ± 8.00 cm vs. 25.5 ± 7.2 cm, P < 0.05) and long jump (203.8 ± 38.9 cm vs. 183.2 ± 33.6 cm, P < 0.05) than national level fencers. Significant differences were observed for drop jump contact time between foil and epee groups (0.32 ± 0.01 ms vs. 0.28 ± 0.01 ms, P < 0.05), respectively. Conclusion The observed differences in anthropometric measurements and leg power performance will facilitate the identification of the most suitable athletes and highlighted specific power abilities that could support the technical drills in competitive fencing. [ABSTRACT FROM AUTHOR]

Objectives Isokinetic-knee-strength was hypothesized to be an important factor related to jumping performance. However, studies examining this relation among elite female athletes and sport-specific jumps are lacking. This investigation determined the influence of isokinetic-knee flexor/extensor strength measures on spike-jump (offensive) and block-jump (defensive) performance among high-level female volleyball players. Design Cross-sectional laboratory study. Methods Eighty-two female volleyball athletes (age = 21.3 ± 3.8 years, height = 175.4 ± 6.76 cm, and weight = 68.29 ± 8.53 kg) volunteered to participate in this study. The studied variables included spike-jump and block-jump performance and a set of isokinetic tests to evaluate the eccentric and concentric strength capacities of the knee extensors (quadriceps – Q), and flexors (hamstring – H) for both legs. Both jumping tests showed high intra-session reliability (ICC of 0.87 and 0.95 for spike-jump and block-jump, respectively). The athletes were clustered into three achievement-groups based on their spike-jump and block-jump performances. Results For the block-jump, ANOVA identified significant differences between achievement-groups for all isokinetic variables except the Right-Q-Eccentric-Strength. When observed for spike-jump, achievement-groups differed significantly in all tests but Right-H-Concentric-Strength. Discriminant canonical analysis showed that the isokinetic-strength variables were more associated with block-jump then spike-jump-performance. The eccentric isokinetic measures were relatively less important determinants of block-jump than for the spike-jump performance. Conclusions Data support the hypothesis of the importance of isokinetic strength measures for the expression of rapid muscular performance in volleyball. The results point to the necessity of the differential approach in sport training for defensive and offensive duties. [ABSTRACT FROM AUTHOR]

Anterior cruciate ligament (ACL) injury prevention programs have been successful in the short term. Motor learning strategies with an internal focus (IF) to body movements have traditionally been utilized, but may be less suitable than an external focus (EF) for the acquisition and control of complex motor skills required for sport. To investigate the available literature and provide an overview of the effect of IF and EF instructions on jump landing technique. Systematic searches were conducted in PubMed (1966 to May 2014), CINAHL (1981 to May 2014) and PsycInfo (1989 to May 2014). A priori defined inclusion criteria were: (i) full text; (ii) published in English, German or Dutch; (iii) healthy adult subjects (mean age ≥18 years); (iv) jump and landing performance tested and (v) study used comparison between an EF and IF. Performance (jump height and distance) and technique (kinematics and kinetics) were the primary outcome variables of interest. Nine papers were included. Significant better motor performance and movement technique was found with an EF compared to an IF. Considering the beneficial results in the included studies when utilizing an EF, it is suggested to implement these strategies into ACL injury prevention programs. [ABSTRACT FROM AUTHOR]

Summary Objective This study was aimed to assess anaerobic capacity after an endurance strength training (EST) protocol for 4 weeks. Methods A group of volunteers ( n = 5) trained in a hypobaric chamber at a simulated altitude of 2500 m (HYP), while the other ( n = 7), trained at sea level (NOR). Anaerobic power was tested before and after the training protocol through the widely used Bosco's vertical jump test procedures: squat jump (SJ), countermovement jump (CMJ) and sixty seconds repeated maximal countermovement vertical jump (60CMJ). The mean height for the whole 60CMJ test (cm), partial heights every 5 and 15 sec were measured and the fatigue index (60CMJ/CMJ] was calculated. Results Hypoxic training significantly improved mean height for 60CMJ by 6.75% ( P = 0.029) in comparison to normoxic training. The fatigue index was also significantly lower ( P = 0.031) in the HYP group than in the NOR group. Partial heights at 45–60” intervals increased by 32.9% in the post-training test for the HYP group ( P = 0.004), compared to a lower improvement of 21.9% for the NOR group ( P = 0.022). Conclusions Our study shows a better anaerobic capacity after EST training at a moderate simulated altitude compared with that attained following the same training protocol at sea level. [ABSTRACT FROM AUTHOR]

We hypothesized that sexual and interspecific differences in jumping performance of fleas found in our previous study are correlated with differences in resting metabolic rate (RMR) between sexes and among species. To test this hypothesis, we measured RMR of seven flea species (Xenopsylla conformis mycerini, Xenopsylla ramesis, Xenopsylla dipodilli, Parapulex chephrenis, Synosternus cleopatrae pyramidis, Nosopsyllus iranus theodori and Stenoponia tripectinata medialis). We compared RMR between sexes and among species and examined whether there is intra- and interspecific correlation between RMR and jumping ability. Both mass-specific and mass-independent RMR were the highest in female S. t. medialis, whereas mass-specific RMR was the lowest in male X. dipodilli and mass-independent RMR was the lowest in three Xenopsylla species and P. chephrenis. Mass-specific and mass-independent RMR were significantly higher in females than in males in all fleas except S. t. medialis. Differences in jumping ability between males and females were found to be correlated with sexual differences in mass-specific or mass-independent RMR. Interspecific comparison showed that the length of jump in both male and female fleas was strongly affected by their mass-specific and mass-independent RMR. [Copyright &y& Elsevier]